Doctors doing a surgery on operating room in hospital

What constitutes major surgery versus a minor procedure?

Case Western Reserve University’s School of Dental Medicine researchers lead multi-disciplinary national study to develop guidelines for patients on blood thinners

While researching how to preemptively manage patients on blood thinners for endodontic surgery last year, dental medicine professor Anita Aminoshariae was surprised to find no clear medical guidelines about what differentiates a major surgery from a minor one. 

“These distinctions matter because it’s a delicate balancing between bleeding too much during a procedure and, god forbid, having a heart attack or stroke before or after a procedure,” Aminoshariae said. “Of course, I’m going to call the physician first. But we should have clear guidelines.”

Their absence prompted Aminoshariae to begin a comprehensive effort to provide them. In late-2020, she rallied a nationwide team of researchers from multiple disciplines to study the issue. They combed through medical databases; consulted the American Heart Association, the American Medical Association and the American Dental Association (ADA); and hand-searched bibliographies of relevant articles and textbooks.

No luck.

“We couldn’t find any consensus among the medical establishment,” she said. “Clinicians should be aware of the best available evidence when considering continuation or discontinuation of antiplatelet and anticoagulant agents perioperatively for endodontic microsurgery. This became even a greater issue with the newer drugs, such as direct oral anticoagulant agents.”

Photo of Anita Aminoshariae
Anita Aminoshariae

The team then turned to medical professionals in other countries, where there are better, well-defined guidelines. Sometimes the formula was as simple as time, Aminoshariae said. For example, in Australia, complicated procedures taking longer than 45 minutes are considered major. In other cases, different factors came into play, such as the invasiveness of the surgery.

In October, Aminoshariae and her colleagues published the results of their odyssey—along with recommendations—in the Journal of Endodontics.

Setting a surgery standard

In the study, the authors called for guidelines for what constitutes a major surgery versus a minor procedure. They also urged creation of an expert panel, drawn from several disciplines including cardiology, pharmacology, oncology, endodontology and physicians to develop clear standards.

“Currently, there are no guidelines,” Aminoshariae said. “Because any minor surgery can become a major surgery, the treating doctor needs to best assess the risk of bleeding, especially if the surgery is anticipated to take longer than 45 minutes. Every patient should be stratified on a case-by-case basis, and consultation with the patient’s physician is highly recommended.”

Aminoshariae was joined in the research by Mark Donaldson, from the School of Pharmacy at the University of Montana and School of Dentistry at the Oregon Health and Sciences University; James Kulild from the University of Missouri-Kansas City; and Dale Baur and Michael Horan from the Case Western Reserve School of Dental Medicine.

For more information, contact Colin McEwen at